Given
#L_1->p=p_1+lambda_1 vec v_1# and
#L_2->p=p_2+lambda_2 vec v_2#
with
#p_1 = (1,-3,0)#
#vec v_1 = (4,1,-1)#
#p_2 = (1,1,1)#
#vec v_2 = (2,0,-1)#
The sought plane #Pi# contains #L_1# and does not contain #L_2#, being parallel to it, so their distance is constant.
Then
#Pi-> p = p_1 + lambda_1 vec v_1 + lambda_2 vec v_2#
And #p_0# the #p_2# projection onto #Pi# is the solution for
#{( p_0 = p_1 + lambda_1 vec v_1 + lambda_2 vec v_2),(
<< p_2-p_0, vec v_1 >> = 0),(
<< p_2-p_0, vec v_2 >> = 0):}#
Giving #lambda_1 = 8/3, lambda_2 = -5#
so #p_0=(5/3, -1/3, 7/3)# and the distance #d = norm(p_2-p_0) = 2#